The subject matter disclosed herein relates to a power system, and more particularly, to calibrating sensors on a power system.
Utility and industrial power systems generally use line-mounted sensors to measure a voltage of a corresponding power line. Generally, these sensors measure the voltage of its respective power line using a capacitive divider method. To use the capacitive divider method, an outer shield or section of the sensor is treated as a first plate of a capacitor (i.e., an outer sensor plate), while earth ground is treated as a second plate of the capacitor such that an effective capacitance (i.e., Cb) exists between the two plates. The outer sensor plate is also capacitively coupled to the conductor itself such that an effective capacitance (i.e., Ca) exists between the conductor and the outer sensor plate. The combination of Ca and Cb form a voltage divider that effectively divides the voltage of the respective power line and results in a lower potential at the node formed between Ca and Cb, which is further processed to determine a line or phase voltage.
Although the capacitive divider method yields a low cost solution for measuring line voltage, the value of Cb can be affected by several factors including soil moisture level, snow, changes in vegetation, and the like, while an effective impedance associated with Ca can be affected by moisture, pollution, ice build-up, and the like. As such, the voltage measurements acquired from these sensors may not reflect accurate voltage levels on the respective lines.